The one piece export brace attaches to the same place as the orginal braces at the firewall side - you might have to drill a couple of new holes depending on what brace you get as the spacing varies (Shelby style braces spread the holes out evenly across the back of the brace). The shock tower ends just sandwich between the shock mounts and the tower or in your case between the upper strut plate and the shock tower using the same three bolt holes that secure the strut plate. Get a Monte Carlo bar too if you don't already have one as the combination of the two parts is much more effective. You should notice a significant difference in the way the car feels with these installed. They really should have been standard equipment.

As Steve said you can cut off the old brace mounts at the shock towers, they don't really weigh anything but you'll gain some work clearance by getting rid of them.

Note too. Somtimes those one peice braces end up being ah little too big where it meets the cowl and may need a little trimmed off the back. Also it's recomended you install it with the car sitting on jack stands just behind the torque boxes,so as to let the front of the car sag down. This can also solve the problem of the brace being too big..